Trait futures_util::sink::SinkExt

pub trait SinkExt<Item>: Sink<Item> {
    fn with<U, Fut, F, E>(self, f: F) -> With<Self, Item, U, Fut, F>
    where
        F: FnMut(U) -> Fut,
        Fut: Future<Output = Result<Item, E>>,
        E: From<Self::Error>,
        Self: Sized,
    { ... }
    fn with_flat_map<U, St, F>(self, f: F) -> WithFlatMap<Self, Item, U, St, F>
    where
        F: FnMut(U) -> St,
        St: Stream<Item = Result<Item, Self::Error>>,
        Self: Sized,
    { ... }
    fn sink_map_err<E, F>(self, f: F) -> SinkMapErr<Self, F>
    where
        F: FnOnce(Self::Error) -> E,
        Self: Sized,
    { ... }
    fn sink_err_into<E>(self) -> SinkErrInto<Self, Item, E>
    where
        Self: Sized,
        Self::Error: Into<E>,
    { ... }
    fn close(&mut self) -> Close<Self, Item>
    where
        Self: Unpin,
    { ... }
    fn fanout<Si>(self, other: Si) -> Fanout<Self, Si>
    where
        Self: Sized,
        Item: Clone,
        Si: Sink<Item, Error = Self::Error>,
    { ... }
    fn flush(&mut self) -> Flush<Self, Item>
    where
        Self: Unpin,
    { ... }
    fn send(&mut self, item: Item) -> Send<Self, Item>
    where
        Self: Unpin,
    { ... }
    fn send_all<'a, St: ?Sized>(
        &'a mut self, 
        stream: &'a mut St
    ) -> SendAll<'a, Self, St>
    where
        St: TryStream<Ok = Item, Error = Self::Error> + Stream + Unpin,
        Self: Unpin,
    { ... }
    fn left_sink<Si2>(self) -> Either<Self, Si2>
    where
        Si2: Sink<Item, Error = Self::Error>,
        Self: Sized,
    { ... }
    fn right_sink<Si1>(self) -> Either<Si1, Self>
    where
        Si1: Sink<Item, Error = Self::Error>,
        Self: Sized,
    { ... }
}

An extension trait for Sinks that provides a variety of convenient combinator functions.

Provided methods

fn with<U, Fut, F, E>(self, f: F) -> With<Self, Item, U, Fut, F> where
    F: FnMut(U) -> Fut,
    Fut: Future<Output = Result<Item, E>>,
    E: From<Self::Error>,
    Self: Sized, 

Composes a function in front of the sink.

This adapter produces a new sink that passes each value through the given function f before sending it to self.

To process each value, f produces a future, which is then polled to completion before passing its result down to the underlying sink. If the future produces an error, that error is returned by the new sink.

Note that this function consumes the given sink, returning a wrapped version, much like Iterator::map.

fn with_flat_map<U, St, F>(self, f: F) -> WithFlatMap<Self, Item, U, St, F> where
    F: FnMut(U) -> St,
    St: Stream<Item = Result<Item, Self::Error>>,
    Self: Sized, 

Composes a function in front of the sink.

This adapter produces a new sink that passes each value through the given function f before sending it to self.

To process each value, f produces a stream, of which each value is passed to the underlying sink. A new value will not be accepted until the stream has been drained

Note that this function consumes the given sink, returning a wrapped version, much like Iterator::flat_map.

Examples

use futures::channel::mpsc;
use futures::sink::SinkExt;
use futures::stream::{self, StreamExt};

let (tx, rx) = mpsc::channel(5);

let mut tx = tx.with_flat_map(|x| {
    stream::iter(vec![Ok(42); x])
});

tx.send(5).await.unwrap();
drop(tx);
let received: Vec<i32> = rx.collect().await;
assert_eq!(received, vec![42, 42, 42, 42, 42]);

fn sink_map_err<E, F>(self, f: F) -> SinkMapErr<Self, F> where
    F: FnOnce(Self::Error) -> E,
    Self: Sized, 

Transforms the error returned by the sink.

fn sink_err_into<E>(self) -> SinkErrInto<Self, Item, E> where
    Self: Sized,
    Self::Error: Into<E>, 

Map this sink's error to a different error type using the Into trait.

If wanting to map errors of a Sink + Stream, use .sink_err_into().err_into().

Important traits for Close<'_, Si, Item>

impl<'_, Si: Sink<Item> + Unpin + ?Sized, Item> Future for Close<'_, Si, Item> type Output = Result<(), Si::Error>;

fn close(&mut self) -> Close<Self, Item> where
    Self: Unpin, 

Close the sink.

fn fanout<Si>(self, other: Si) -> Fanout<Self, Si> where
    Self: Sized,
    Item: Clone,
    Si: Sink<Item, Error = Self::Error>, 

Fanout items to multiple sinks.

This adapter clones each incoming item and forwards it to both this as well as the other sink at the same time.

Important traits for Flush<'_, Si, Item>

impl<'_, Si: Sink<Item> + Unpin + ?Sized, Item> Future for Flush<'_, Si, Item> type Output = Result<(), Si::Error>;

fn flush(&mut self) -> Flush<Self, Item> where
    Self: Unpin, 

Flush the sync, processing all pending items.

This adapter is intended to be used when you want to stop sending to the sink until all current requests are processed.

Important traits for Send<'_, Si, Item>

impl<'_, Si: Sink<Item> + Unpin + ?Sized, Item> Future for Send<'_, Si, Item> type Output = Result<(), Si::Error>;

fn send(&mut self, item: Item) -> Send<Self, Item> where
    Self: Unpin, 

A future that completes after the given item has been fully processed into the sink, including flushing.

Note that, because of the flushing requirement, it is usually better to batch together items to send via send_all, rather than flushing between each item.

Important traits for SendAll<'_, Si, St>

impl<'_, Si: ?Sized, St: ?Sized, Ok, Error> Future for SendAll<'_, Si, St> where
    Si: Sink<Ok, Error = Error> + Unpin,
    St: Stream<Item = Result<Ok, Error>> + Unpin,  type Output = Result<(), Error>;

fn send_all<'a, St: ?Sized>(
    &'a mut self,
    stream: &'a mut St
) -> SendAll<'a, Self, St> where
    St: TryStream<Ok = Item, Error = Self::Error> + Stream + Unpin,
    Self: Unpin, 

A future that completes after the given stream has been fully processed into the sink, including flushing.

This future will drive the stream to keep producing items until it is exhausted, sending each item to the sink. It will complete once both the stream is exhausted, the sink has received all items, and the sink has been flushed. Note that the sink is not closed.

Doing sink.send_all(stream) is roughly equivalent to stream.forward(sink). The returned future will exhaust all items from stream and send them to self.

Important traits for Either<A, B>

impl<A, B> Future for Either<A, B> where
    A: Future,
    B: Future<Output = A::Output>,  type Output = A::Output;

fn left_sink<Si2>(self) -> Either<Self, Si2> where
    Si2: Sink<Item, Error = Self::Error>,
    Self: Sized, 

Wrap this sink in an Either sink, making it the left-hand variant of that Either.

This can be used in combination with the right_sink method to write if statements that evaluate to different streams in different branches.

Important traits for Either<A, B>

impl<A, B> Future for Either<A, B> where
    A: Future,
    B: Future<Output = A::Output>,  type Output = A::Output;

fn right_sink<Si1>(self) -> Either<Si1, Self> where
    Si1: Sink<Item, Error = Self::Error>,
    Self: Sized, 

Wrap this stream in an Either stream, making it the right-hand variant of that Either.

This can be used in combination with the left_sink method to write if statements that evaluate to different streams in different branches.

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Implementors

impl<T: ?Sized, Item> SinkExt<Item> for T where
    T: Sink<Item>, 

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